Steel for high temperature service



June 11, 1946. E. c. WRIGHT STEEL FOR HIGH TEMPERATURE SERVICE Filed April 7, 1943 EREEP STRENGTH FUR 1% ELDNEATICIN IN 'HlUUIJHnuns BUD I sun TEMPERATURE -.F'

'lElEIEI INVENTOR. EDW/IV K W/6H7', F a ZuJ Patented June 11, 1946 STEEL FOR HIGH TEMPERATURE SERVICE Edwin C. Wright, Beaver, Pa., assignor to National Tube Company, a corporation of New Jersey Application April 7, 1943, Serial No. 482,164

I 2 Claims.

A steel containing considerable amounts of phosphorus and having a very low oxygen content in iron combined form has certain desirable physical properties, and is disclosed and claimed in a separate application bearing Serial No. 445,977 and filed'June 5, 1942. Further study of of short-time high temperature tensile tests and long-time flow or creep tests, indicated that phosphorus imparted considerable strength to the steel at elevated temperatures. Since it is further well known that additions of molybdenum to carbon steels also increases the strength of the steel at high temperatures. special steels having a low oxygen content in iron combined form were prepared with varying amounts of phosphorus and molybdenum. Tests of these steels at high temperatures show clearly that phosphorus and molybdenum additions supplement the respective eflect each of these alloys and that the steels heated with both phosphorus and molybdenum additions have high strength at elevated temperatures.

The typical composition of these steels is as follows:

Carbon .15- .30 Manganese .30-2.00 Phosphorus .10- .30 Molybdenum .25-2.00 Silicon .15 .50 Sulphur .05 max. Oxygen as F'eO under .01.

- this type of steel at high temperatures by means rus are definitely superior to the molybdenum steels with low phosphorus in the important operating temperature range of 800 F. to 1000 F. Although phosphorus-molybdenum steels covered by this application have shown very desirable high temperature properties, it has been further developed that if the steels containing from .10 to .30 phosphorus are so treated that the oxygen in iron combined form is reduced to a very low level, the steels are tough and remain tough after long exposure to high temperature service. Investigations of specimens which have been under creep test for at least 3,000 hours show that the ductility and impact toughness of the material after being under stress of 800 to 1000 F. had not decreased.

The increase in load carrying capacity at 1000 F. permits the use of lighter sections. or it sections of equal weight are used, a high factor of safety will be obtained.

I claim: I

1. An article which in use is subjected to stress at elevated temperatures above about 800 F.

.and made of steel of the molybdenum containing type designed for elevated temperature service and characterized by containing sufficient phosphorus to materially increase its high temperature creep strength as compared to said strength in the case of the same type of steel with a lesser phosphorus content but otherwise of similar composition, the steel containing less than .01% oxygen combined with iron whereby its toughness is enhanced throughout long service at elevated temperature.

2. An article which in use is subjected to stress at elevated temperatures above about 800 F. and made of steel containing from .15 to .30% carbon, from .30 to 200% manganese, from .10 to 30% 'phospho ,from .25 to 2.00% molybdenum, from .15 to .50% silicon and not more than .05%' sulphur, with'the balance substantially all iron with .less than .01% oxygen combined with the iron. r

I EDWIN C. WRIGHT. 

